Garbage disposals are electrically-powered devices that may be installed under a sink for disposing of food waste. For example, a user can rinse shredded food waste down a kitchen sink when cleaning dishes, rather than stopping to scrape food waste into a garbage can. A kitchen garbage disposal shreds the food waste into small pieces to enable the passage of the food waste through the waste piping system that connects the kitchen drain, to which the garbage disposal is attached, to a municipal sewer system or septic tank.
FIG. 1A shows a side view of an exemplary garbage disposal installed under a sink. A garbage disposal 100 is attached to a sink 102 and positioned between a dishwasher drain hose 104 and a piping U-bend 106. FIG. 1B shows a cross-sectional view of the garbage disposal shown in FIG. 1A. Food waste is shred in the garbage disposal 100 by a shredder ring 108 which is powered by a motor 110. Food waste is deposited through a flanged opening 112, into an upper chamber 114 of the garbage disposal 100, and drops onto a turntable 116. When the garbage disposal is turned on, food waste is forced outward by centrifugal forces to the perimeter of the turntable 116 and against the shredder ring 108. The shredder ring 108 includes a number of notches with sharp edges for cutting. Two hammers 118 and 120, loosely attached to the turntable 116 to allow for movement of the hammers on the turntable 116, assist in forcing food waste through the shredder ring 108. The notches of the shredder ring 106 shave food waste into small chips that fall into the lower chamber 122 of the garbage disposal. A constant flow of water from a kitchen sink discharges the shredded food waste from the lower chamber 122, out through a disposal outlet 124, and into the waste piping system of a building. However, the discharge of shredded food waste from a garbage disposal into the waste piping system of a building may result in blocking and back-ups in the piping systems, and overloading of municipal sewer systems.
Some waste piping systems are connected to septic systems, which are small-scale sewage treatment systems that are common in areas with no connection to a municipal sewage system. FIG. 2 shows a side view of a septic system located adjacent to a residence. A septic system 200 includes a septic tank 202 attached to a drainage field 204 for disposal of treated wastewater (“effluent”) 206. Wastewater from utilities, such as a toilet 208, a shower 210, and a sink 212, flows through an underground septic-tank-wastewater inlet pipe 214 to a septic tank 202 that includes a first chamber 216 and a second chamber 218. Wastewater in the septic tank 202 flows into the first chamber 216, depositing solid particles that, over time, create a sludge layer 220. Anaerobic bacteria continuously decompose the sludge layer 220, slowing the build-up of sludge in the first chamber 216 of the septic tank 202.
FIG. 3 shows a cross-sectional view of the septic tank from the septic system shown in FIG. 2. The first chamber 216 and second chamber 218 of the septic tank 202 are formed by a dividing wall 302 that includes an opening 306 located about midway between the top and bottom of the septic tank 202. After a sludge layer 220 is formed in a first chamber 216 of the septic tank 202, the liquid component of the wastewater flows through the dividing wall 302 into the second chamber 218 where further settlement of solid particles takes place, creating a second sludge layer 306. Finally, the wastewater flows through an effluent filter 308 and is disposed of as effluent 206 through the piping network of the drainage field 204, as shown in FIG. 2.
When a septic system is treating wastewater that includes shredded food waste from a garbage disposal, sludge layers can rapidly accumulate, and anaerobic bacteria may be unable to adequately slow down the build-up of the sludge layers 220 and 306. An increased rate of sludge deposition may eventually block the flow of wastewater through a dividing wall 302 and result in failure of the septic system 200. Shredded food waste from a garbage disposal can also create oil-in-water emulsions, causing build-up and eventual blockage of piping and drainage fields. Consequently, some communities have banned the use of garbage disposals in buildings connected to septic systems.
The controlled decomposition of organic matter under aerobic conditions, one form of composting, is an alternative method for disposing of food waste. Composting can be performed by various organisms, including microorganisms, and invertebrates such as, nematodes, and worms. One type of composting, referred to as “vermicomposting,” produces compost from food waste by using a species of worms adapted to composting, such as Brandling Worms (Eisenia foetida) or Redworms (Lumbricus rubellus). The addition of Brandling Worms or Redworms can accelerate the composting process. FIG. 4 shows a exploded view of a vermicomposting bin. A continuous-vertical-flow vermicomposting bin (“bin”) 400 for disposing of food waste includes a vertically stacked series of composting trays 402, 404 and 406 above a collection tray 408. A user loads the bin 400 by adding a layer of bedding material to the bottom of the first composting tray 402, and then adding worms and organic matter in another layer. An additional layer of bedding material is then added on top of the layer of worms and organic matter. The second composting tray 404 is first filled with organic matter followed by a layer of bedding material. The third composting tray 406 is filled with organic matter.
During operation, the collection tray 408 catches excess liquid that is produced during the decomposition process and that is drained through a spout 412. Holes 414 and 416 in the top of the bin 400, and on the bottom of the composting trays 402, 404 and 406, allow air to flow through the bin. The bin 400 operates by the ascending vertical migration of worms from the first composting tray 402 up to the third composting tray 406. Worms 410 added to the first composting tray 402 migrate upward towards the layers of organic matter, a food source, after composting the layer of organic matter in the first composting tray 402, and second composting tray 404. After the worms 410 have migrated upward from a first or second composting tray, the first or second composting tray contains composted organic material that can be collected. At the end of operation, many of the worms 410 have migrated to the third composting tray 406, and can be removed when the organic matter layer in the third composting tray 406 has been decomposed.
Maintaining optimum conditions for worms in a vermicomposting bin can be difficult, as worms are adapted to specific conditions in soils. Worms used in composting prefer temperatures of between fifty-five to seventy-five degrees Fahrenheit and can die in temperatures below freezing or above ninety degrees Fahrenheit. Users may also find it difficult to maintain a continuous-vertical-flow vermicomposting bin stored outside due to fluctuations in temperature and moisture. Odors may be produced by continuous-vertical-flow vermicomposting bins, and may attract organisms that spread pathogens, such as rats, and undesirable insects, such as flies. As a result, users often chose to store bins outside. However, vermicomposting worms do not thrive in unregulated environments. Worms prefer food waste to be macerated or partially decomposed prior to ingestion. Users often lack time and interest to macerate the food waste prior to loading a continuous-vertical-flow vermicomposting bin to speed the composting process. Users need also to regularly inspect and adjust moisture levels so that worms and microorganisms can rapidly degrade food waste. Users, manufacturers, and vendors of food waste disposal systems have, therefore, recognized a need for a food waste disposal system that can efficiently dispose of food waste, while also minimizing the negative impacts on municipal and private sewer treatment systems.